//
// Copyright (c) 2008 Novell, Inc. (http://www.novell.com)
//
// Permission is hereby granted, free of charge, to any person obtaining
// a copy of this software and associated documentation files (the
// "Software"), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, sublicense, and/or sell copies of the Software, and to
// permit persons to whom the Software is furnished to do so, subject to
// the following conditions:
//
// The above copyright notice and this permission notice shall be
// included in all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
// EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
// NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
// LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
// OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
// WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
//

using System;
using System.Collections.Generic;

namespace DotnetSpider.HtmlAgilityPack.Css;
// Adapted from Mono Rocks

internal abstract class Either<TA, TB>
    : IEquatable<Either<TA, TB>>
{
    private Either() { }

    public static Either<TA, TB> A(TA value)
    {
        if (value == null) throw new ArgumentNullException("value");
        return new AImpl(value);
    }

    public static Either<TA, TB> B(TB value)
    {
        if (value == null) throw new ArgumentNullException("value");
        return new BImpl(value);
    }

    public abstract override bool Equals(object obj);
    public abstract bool Equals(Either<TA, TB> obj);
    public abstract override int GetHashCode();
    public abstract override string ToString();
    public abstract TResult Fold<TResult>(Func<TA, TResult> a, Func<TB, TResult> b);

    private sealed class AImpl(TA value) : Either<TA, TB>
    {
        private readonly TA _value = value;

        public override int GetHashCode()
        {
            return _value.GetHashCode();
        }

        public override bool Equals(object obj)
        {
            return Equals(obj as AImpl);
        }

        public override bool Equals(Either<TA, TB> obj)
        {
            return obj is AImpl a
                   && EqualityComparer<TA>.Default.Equals(_value, a._value);
        }

        public override TResult Fold<TResult>(Func<TA, TResult> a, Func<TB, TResult> b)
        {
            if (a == null) throw new ArgumentNullException("a");
            if (b == null) throw new ArgumentNullException("b");
            return a(_value);
        }

        public override string ToString()
        {
            return _value.ToString();
        }
    }

    private sealed class BImpl(TB value) : Either<TA, TB>
    {
        private readonly TB _value = value;

        public override int GetHashCode()
        {
            return _value.GetHashCode();
        }

        public override bool Equals(object obj)
        {
            return Equals(obj as BImpl);
        }

        public override bool Equals(Either<TA, TB> obj)
        {
            return obj is BImpl b
                   && EqualityComparer<TB>.Default.Equals(_value, b._value);
        }

        public override TResult Fold<TResult>(Func<TA, TResult> a, Func<TB, TResult> b)
        {
            if (a == null) throw new ArgumentNullException("a");
            if (b == null) throw new ArgumentNullException("b");
            return b(_value);
        }

        public override string ToString()
        {
            return _value.ToString();
        }
    }
}